Coke burning method



March 14, 1944.

F. R. SCHRAGE 2,344,328 COKE-BURNING METHOD Filed April 17, 1940 Room I[gq'kermoatmt Time switch .J v I v l. L I J I l g 3/ Hank/in R Sch aywill? 5' Patented Mar. 14, 1944 UNITED Y-STATESPATENT OFFICE COKEBURNING METHOD Franklin R. Schrage, Riverside, Ill., assignor toInterlake Iron Corporation, Chicago, 111., a corporation of New York vApplication April 17, 1940, Serial No. 330,152

, 1 Claim. (Cl. 110-1) This invention'relates to the burning of coke, '4

and particularly to the burning of coke in domestic furnaces such as areemployed for heating purposes.

Coke has been found to be an excellentv fuel for domestic heatingpurposes because of its comparative cleanliness ascompared with manytypes of coal and because of its low cost as compared-with fuel oil andthe more expensive forms of. coal. Coke, however, as compared with coalandfuel oil, has the disadvantage that it is difficult to operate afurnace automatically with it. Because of its high ignition temperature,it is generally impractical to burn coke in the ordinary domestic typeof underfeed stoker. Overfeed stokers have been constructed by means ofwhich coke is automatically deposited on top of the fire bed asrequired, in simulation to hand firing, and stokers of this type, whenused in connection with thermostatically controlled furnace dampers,have provided a practical semi-automatic way .of firing domesticfurnaces with coke. However, arrangements of this type have requireddaily attention to the fire in order to maintain proper draftconditions, and the variation in the temperature of the building beingheated has been considerably greater than desirable because of theslowness of the response of the fire to the draft controls. v a

One of the principal objects of this invention is to provide a method ofburning coke in domestic furnaces which will be almost completelyautomatic in operation and require the minimum of attention.

Another object of this invention is to provide I a method for burningcoke which will operate not only "with lumps of coke having'a maximumdimension of two or three inches but also with coke in much smallerpieces 01 particles such as are now considered unsuitablefor use indomestic furnaces. V

A The novel features which I believe to be characteristic of myinvention are set forth with particularity in the appended claim. Myinvention itself, however, both as to its organization and manner ofconstruction, together with further objects and advantages thereof, maybest be understood by reference to the following-description taken inconnection with the accompanying drawing, in which:

I Figure l is a side view, partly in elevation, partly in section, andpartly diagrammatic, of one of the preferred arrangements of equipmentfor carrying-outthe invention; and- Figure 2 is a cross section on theline IIII of Figure 1.

While the invention may be carried out in practice in numerous differentways, I have shown, by

1 way of illustration, a particular installation which comprises aconventional domestic boiler l0 having water spaces surrounding the firepot 2. The bottom of the fire pot is provided with a grate l3 which alsoforms the top of the ash pit l4 under the firepot. Access to theinterior of the firepot I2 is provided by a door opening in the side,and access to the ash pit I4 is provided by an ash pit door opening I6.The grate l3, which is formed of separate grate bars arranged in ahorizontal plane, may be provided with a supplementary conical grate Hwhich is located in the center of the main grate l3. The conical grateI1 is formed of a heat-resisting iron casting and is provided with aplurality of apertures |8 therethrough for permitting the passage ofair.

The boiler I0 is provided with a flue or pipe l9 for carrying theproducts of combustion to a chimney, and the pipe or flue l9 containstwo butterfly dampers 20 and 2| spaced along its length and has a checkdamper 22 located on-the side between the two butterfly dampers 20 and2|. As may be seen from Figure 2, the butterfly dampers 20 and 2|, whichare alike, are each formed with a central aperture 23, so that they willnot entirely close off the flue l9 even when they are in their fullyclosed positions.

A stoker 24 of the overfeed type is provided for automatically feedingthe coke, which is used as fuel, to the fire. The stoker 24 may be anystoker of the type which feeds fuel to the top of the fire and whichwill maintain the top of the fire bed at a predetermined level. Theparticular stoker shown in the drawing for the purpose of illustrationis a Murray stoker, Model No. 40., and comprises a stand 25 mounted uponwheels 26 so that the entire stoker 24 can be readily moved away fromthe boiler Ill when desired. The stand 25 supports a hopper 21containing the coke 28 to be burned, and also supports, below thehopper, a mechanism 29 for introducing the coke into the furnace.

The coke-feeding mechanism 29 projects through the door opening I5 ofthe boiler and is provided with a plate 30 which closes the opening I5,the door for the opening I5 either being removed or swung out of theway;

The coke-feeding mechanism 29 includes a heavy fire-resistant controlmember 3|, which normally rests upon the top of the fire and which isarranged to set the feeding mechanism into operation whenever the fireburns down and allows the member 3! to drop below a predetermined level.When this occurs, the control member 3| is lifted up out of the way, theshovel portion 32 of the mechanism moves in to the center of the firepot, and an ejector forces fuel out of the extended shovel 32 onto thetop of the fire. The parts then return to their former positions untilthe top of the fire bed again drops below the predetermined level.

Means are provided for supplying a forced draft to the boiler, and forautomatically controlling the draft in accordance with the heatingrequirements. These means comprise a blower 34, which may be of thecentrifugal type as shown, driven by a suitable electric motor 35, andmounted upon a plate 36 covering the ash pit door opening 16. The inlet31 to the blower34 is provided with a shutter 38 by means of which theeffective area of the inlet opening 31 may be varied as desired in orderto adjust the capacity of the blower 34.

The blower motor 35 is provided with electric power through a set ofcontrols which includes a thermostat 39 placed in the space which isbeing heated by the boiler Ill, a limit control or switch 40, which isresponsive to the temperature of the water or steam by means of whichthe heat is transferredfrom the boiler to the space to be heated, and atime switch 4! connected to each other and to the motor 35 and to asource of power by wires 42, 43, 45, and 45. The thermostat 39 isarranged to allow the blower motor 35 to be energized whenever thetemperature in the space to be heated drops below a predeterminedtemperature, such as '70 degrees Fahrenheit. The limit control 40 isarranged to cut off the power to the blower motor 35 whenever thetemperature of the water or the pressure of the steam rises above apredetermined safe point, irrespective of whether the thermostat 39 iscalling for more heat or not. The time switch 4| contains a clockwork orother time-keeping mechanism and is arranged to energize the blowermotor 35 for a few minutes at comparative long intervals of time, suchas every hour. If desired, the time switch may be of the type thatoperates in conjunction with the thermostat so that a full interval oftime, such as one hour, will intervene between the shutting ofi of theblower motor 35 by the thermostat and its energization by the timeswitch.

The set of controls which has been illustrated is of the so-called highvoltage type, each control making or breaking the circuit for the blowermotor'35. If desired, however, other suitable means may be provided formaking and breaking the circuit, for the blower motor 35, withoutdeparting from the spirit and scope of the present invention.

In carrying out the teachings of the novel method, a bed of ashes 41,which is preferably from three to five inches in depth, is first formedon top of the grates l3 and IT. The ashes may be secured from anexternal source and spread over the grates to the desired depth, or afire may be built in the boiler in the conventional manner and allowedto burn down to ashes if no convenient supply of ashes is at hand. Acoke fire is then built on top of the ashes 4'! and, when this forms alayer of burning coke 48, it is covered by a layer of fresh coke 49.There is thus formed a fire bed composed of a layer of ashes 41, a layerof burning coke 48, and a layer of unburned coke 49 arranged one abovethe other. After the fire bed has been formed in this manner, the twobutterfly dampers 20 and 2! in the furnace flue l9 are placed in theirclosed position, as shown in the drawing, and the check damper 22 isopened. Thus there is substantially no natural draft acting on the fire.

Because of the almost complete absence of natural draft, the fire burnsvery slowly when the blower 34 is not operating and consumes very littlecoke. When the blower 34 is set into operation by the thermostat 39 orthe time switch 4|, a substantial amount of air is forced through thefire bed and the layer of burning coke 48 burns briskly. Under theseconditions of operation, that is, alternate quiescence and briskcombustion, a large porous clinker 50 is formed between the bed of ashes41 and the layer of burning coke 48, the clinker being formed from theincombustible residue of the burnt coke. The clinker 50 is annular inshape, this shape apparently being caused by the radially outwardmovement of the burning coke 48 above the conical grate l1.

As the system continues in operation, the thickness of the clinker 50increases and the area ofits central opening decreases, and both ofthese changes increase the resistance to the fiow of air through thefire bed. The shutter 38 on the blower is therefore adjusted from timeto time in order to maintain the desired-flow of air and rate ofcombustion. Eventually, the clinker 50 so obstructs the flow of air thatthe desired rate of combusion cannot be maintained even when the shutter38 on the blower is fully opened. It is' then necessary to break up andremove the clinker 50, which is readily done by means of apoker'inserted through the door opening I5, the stoker 24 being rolledback out of the way while this operation is being performed. Aftertheclinker 50 has been removed, combustion proceeds as before and anotherclinker 50 starts to form.

It has been found, by actual operation of the above-described systemover a period of months, that breaking up and removal of the clinker 50is necessary only at intervals of once or twice a week depending on therate of combustion. It is thus practical to allow the system to functionunattended in moderately cold weather, except for supplying coke' 28 tothe hopper 21 and adjusting the blower shutter 38, over intervals of aweek, and an even temperature of the space being heated will beautomatically maintained. Because of the almost complete stopping ofcombustion when the blower 34 is not operating, the system generatesvery little heat after the thermostat ceases to call for heat, and avery even temperature is maintained in the space being heated. It hasbeen found, for example, that the temperature of a heated space willvary less than one degree from the desired temperature as long as thesystem is kept in operation.

It has been found that the above-described system for burning cokewilloperate satisfac torily with coke in much smaller pieces than isordinarily used for domestic heating purposes. and that the system willeven operate with powdered coke known as coke breeze. Because the cokeis fed onto the top of the fire bed, the layer of unburned coke 49forms, as it were, a filter which holds down whatever small particles ofburning coke may be present and prevents any such particles or particlesof ash from being blown up out of the fire bed by the draft. Thus.

not only is the system capable of operating with coke in the form ofsmall particles but it operates without the production of any fly ash.

Another advantage of the system of burning coke which has been describedabove is the almost complete elimination of the problem of ash\rem-oval, While the system is in operation, additional ash is formed atsuch a slow rate that it is not necessary to shake the grate l3 morethan once or twice a year in order to keep the bed of ashes 41 at thedesired thickness. The incombustible matter in the coke accumulates inthe clinker 50, as previously mentioned, and the clinker 50 can bewithdrawn from the fire and disposed of without the creation of anydust, as contrasted to the removal of ashes produced by conventionalsystems of burning coke. While I have shown only one arrangement ofapparatus for carrying out my invention, it will, of course, be clearthat numerous modifications and changes may be made. Other forms ofblowers than the one shown may be used, as long as the blower is capableof maintaining a static pressure that reaches a maximum of one-quarterof an inch of water in the ash pit when the clinker 50 is at its maximumpermissible thickness. The conical grate ll may be omitted, but I havefound it preferable to employ this grate because it results in theformation of an annular clinker, which is more easily removed than thedisc clinker which would otherwise be formed. Other forms of stokers maybe used as long as they are of the same general type, and the firing ofthe coke may even be done by hand although the latter procedure is atthe expense of some of the chief advantages of my system. The furnace l0may be a boiler, as shown, or may be a hotair or other form of furnace,and the controls may obviously be varied somewhat from those shown. Itherefore do not intend to limit the patent granted hereon to thespecific method which I have shown and described, but it is to beclearly understood that it embraces all methods falling within the termsof the following claim.

I claim as my invention:

A method of burning coke in a furnace which comprises forming a fire bedhaving a layer of ashes and a layer of burning coke above the ashes anda layer of unburned coke above the burning coke, and alternatelymaintaining a low draft and a high draft through said fire bed, said lowdraft being scarcely sufficient to maintain combustion of said coke andsaid high draft being sufficient to maintain combustion of said coke ata temperature above the clinker-forming temperature.

FRANKLIN R. SCI-IRAGE.

